The striker was substituted early on in the Champions League final after suffering a torn hamstring but the Spain boss has revealed he is progressing well in training
The Atletico Madrid forward tore his hamstring in his side's Champions League final defeat to Real Madrid, which has resulted in Del Bosque delaying finalising his 23-man squad - and he may even wait until the Fifa deadline on June 2.Del Bosque had earlier conceded he "wasn't sure" whether the 25-year-old would be fit for Brazil but he has now revealed both the striker and Jesus Navas are showing encouraging signs in their efforts to return to fitness.
"It looks promising. On Friday they will have a scan. If it's good, we will make a decision on Saturday morning," he told a press conference on Friday.
Costa was the subject of much controversy when he opted to play for Spain rather than Brazil back in March.
He made two friendly appearances for the Selecao in 2013 before making his international debut for Del Bosque's men against Italy.
Costa will not feature for Spain in friday's friendly with Bolivia, meaning Fernando Torres is in line to stake his claim for a World Cup spot.